Socioeconomic determinants of re/afforestation efforts

Meeting the Paris Agreements’ climate target will require the large-scale deployment of Carbon Dioxide Removal (CDR) methods. Afforestation/reforestation (A/R) has been widely practiced and constitutes virtually all of CDR applied so far. However, implementing large scale A/R strongly depends on biophysical conditions and socioeconomic contexts defining the likelihood for implementation as well as maintenance of an A/R project. To date, biophysical enabling and constraining conditions have been extensively investigated, but studies on socioeconomic determinants remain largely confined to local scales and are primarily in the forms of qualitative evaluations. Hence, we lack a unified global understanding of socio-economic factors that have determined A/R success so far, despite the large potential of drawing on the growing database of global spatially explicit socioeconomic dimensions for a more comprehensive assessment. Here, we use machine learning to leverage multiple data streams and to explore why some countries succeed in A/R efforts while others fall short. We show that a country is likely to achieve better A/R outcomes (both in terms of absolute area and ratio of planted forest) when it has lower poverty rate, lower relative implementation cost and lower food insecurity, as well as strong institutions, adequate infrastructure and social acceptance of A/R. Economic factors (poverty, food security, implementation cost, forest road and workforce) play a key role in predicting A/R outcomes (accounting for ~70% of the relative importance), and institutional factors (governance and land tenure) contribute around 20%, while social factors (social acceptance and land use decision making) contribute only marginally (~10% ). Our  analysis revealed that a considerable number of countries–particularly in tropical regions–have significant potential but simultaneously face multiple socioeconomic constraints to upscaling implementation and maintaining the carbon sink. Our findings suggest that the A/R-based CDR potential could be overestimated when such socioeconomic barriers are not considered. This is likely the case in future scenarios generated by Integrated Assessment Models, as they typically do not explicitly consider many social, institutional and ethics-related factors. Our results suggest key entry points for effective mitigation policy that alleviates socioeconomic barriers, in particular via fighting poverty. Our study complements the extensive literature base on biophysical constraints to CDR by a unique compilation of the existing global datasets on socioeconomic determinants. This provides a vastly expanded basis of factors that can be considered when assessing the implementation likelihood and permanence of A/R and can guide the design of pathways that not only operate within safe socioeconomic boundaries, but also realizes the biophysical potential of CO₂ removal.